For an existing three-dimension (3D) display technology, usually a parallax baffle 20′ (i.e., a slit grating) is arranged at a display side of a display panel 10′, so as to achieve the 3D display. FIG. 1 shows the principle thereof, in which the parallax baffle 20′ has slit gratings, and images of pixels on the display panel 10′ are transmitted to a viewpoint through the slits on the parallax baffle 20′. As shown in FIG. 1, at the viewpoint, different pixels on the display panel 10′ may be observed by a viewer's left eye 12′ and right eye 11′, so that the viewer can merely observe a left-eye image by the left eye and the a right-eye image by the right eye at the viewpoint. The left-eye and right-eye images are then combined in the viewer's brain to obtain a stereo effect.
Along with the development of the market, a 2D/3D switchable display device appears. In order to switch between a 2D display mode and a 3D display mode, a liquid crystal slit grating is a most commonly used technique. As a shown in FIG. 2, the liquid crystal slit grating may be a TN-mode liquid crystal panel and include, from top to bottom, an upper polarizer 30′, an upper substrate 100′ and a lower substrate 200′ arranged oppositely to each other to form a cell, a lower polarizer 31′, and a liquid crystal layer 60′ arranged between the upper substrate 100′ and the lower substrate 200′. The upper polarizer 30′ is of a polarization direction identical to the lower polarizer 31′. A plurality of parallel, bar-like transparent electrodes 40′ are formed at a surface of the upper substrate 100′ close to the liquid crystal layer 60′, and a gap between the adjacent transparent electrodes 40′ meets the requirement of the slit grating for autostereoscopic 3D display. Plate-like transparent electrode 41′ are formed at an entire surface of the lower substrate 200′ close to the liquid crystal layer 60′. The bar-like transparent electrodes 40′ and the plate-like transparent electrodes 41′ are electrically connected to two ends of a power source 50′, respectively, and a switch 70′ is provided so as to control whether or not to apply voltages to the bar-like transparent electrodes 40′ and the plate-like transparent electrodes 41′. To be specific, when the switch 70′ is turned on and no voltage is applied to the bar-like transparent electrodes 40′ and the plate-like transparent electrodes 41′, liquid crystal molecules of the liquid crystal layer 60′ are not deflected so as to allow the transmission of the light therethrough, thereby to achieve the 2D display. When the switch 70′ is turned off and the voltages are applied to the bar-like transparent electrodes 40′ and the plate-like transparent electrodes 41′, the liquid crystal molecules at a region corresponding to the bar-like transparent electrodes 40′ are deflected so as to form light-shielding stripes through which the light cannot be transmitted. At this time, the light can merely be transmitted through light-transmitting stripes between the bar-like electrodes, so as to achieve the 3D display.
However, the process for manufacturing the liquid crystal slit grating is complex, and the production cost thereof is relatively high, so it is adverse to lightening and thinning of the 2D/3D switchable display device as well as the promotion thereof. In addition, the polarizers provided in the liquid crystal slit grating may also reduce the light utilization rate.